Electric furnace.



Patented Dec; 9, |902.

H. N. POTTER.

ELECTRIC FURNACE.

[Application filed Mar. 27, 1902.:

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UNITED STATES PATENT OEEICE.

HENRY NOEL POTTER, OF NEW ROCHELLE, NEW YORK, ASSIGNOR TO GEORGEWESTINGI-IOUSE, OF PITTSBURG, PENNSYLVANIA.

ELECTRIC FU RNACE.

SPECIFICATION forming part of Letters Patent No. 715,508, dated December9, 1902.

Application led March 2 7. 1 9 02 .T0 all whom, t may cm1/067%:

Be it known that I, HENRY NOEL POTTER, a citizen of the United States,and a resident of New Rochelle, in the county of Westchester and Stateof New York, have invented cer-v tain new and useful Improvements inElectric Tube- Furnaces, of which the following is a specication. v

In an application filed by me on the 21st day of November, 1901, SerialNo. 83,078, I show and describe a lined carbon furnacetube in. which thetube rotates about its axis in order that the melted lining material mayiiow evenly over the inner surface of the carbon tube, while thatinvention also contemplates the rotation of the furnace-tube for otherpurposes, as when metallic chromium is produced by a continuousoperation and the material is worked steadily through the furnace partlyby the eifects of the rotation of the tube.

The present invention contemplates making the furnace of a double tube,an outer and an inner tube, the outer being an electrical conductorprovided with terminals in any suitable manner and the inner being acomparatively thin walled tube of such diameter as to permit itsrotation within the outer tube. By rotating the inner tube upon its axismany of the effects produced by rotating the entire furnace are securedand some additional advantages are obtained. Thus when the furnace ismade according to my present invention the inner tube or the part of thefurnace most subject to wear can be easily renewed. Moreover, since thefurnace itself is not rotated the terminals will also be stationary, andtheir construction can be modified so as to allow them to beWater-cooled. The annular space between the inner and the outer tubesmay be iilled with an inert gas, though in practice the oxygen of theair in the limited space between the tubes would soon be taken up andwould in most cases do little or no injury. If a special gas is used,however, it would usually be hydrogemthough for certain purposesnitrogen might be used.

The stationary tube will generally be of carbon, and the inner tube maybe either of car- Serial No. 100,161. (No model.)

bon, lined or unlined, or of a material such 5o as magnesia, zirconia,or the like.

I prefer to let both the tubes project axially beyond the terminals tosuch a distance as shall allow them to become reasonably cool, so as tofacilitate the attachment of metal or other tubes to convey the inertgas. Moreover, I propose to extend the idea of watercooling to theprojecting ends of the tubes and in certain cases to the supportingcollars which are fully described in my application 6o referred to aboveand also in the present application.

Hitherto I have proposed the use ot' a cylin drical tube; but forcertain purposes, particularly those where high temperatures are notnecessary, a conical tube has advantages. v For example, a tight fitbetween the conical lining and the tube can always be secured withoutthe necessity of fusing the lining to the carbon tube by simply pushingthe lining 7o into the carbon tube when the lining shrinks.

In such cases it is advantageous to make the tube of magnesia, Zirconia,or the like, coustituting the lining somewhat longer than the carbonfurnace-tube. At the large end, however, the lining-tube should cease tobe conical and become cylindrical, with an outer diameter equal to thelargest bore of the carbon tube.

For operations such as tempering steel, ir- 8o ing enamel, and makingalloys the advantages of having an inner rotating carbon tube can besecured without the use of the latter by merely having a rotatingmagnesia lining, the temperature not being sufficiently high to causethe lining to adhere to the carbon furnace-walls.l

My invention is illustrated in the accompanying drawings, in which-Figure l is a longitudinal section of my im- 9o proved furnace with aninner carbon tube adapted to rotate within the main furnacetube. Fig. 2is a cross-section of the same furnace. Fig. 3 is a longitudinal sectionot' a portion of a similar furnace, in which, however, the inner carbontube is provided'with a lining of magnesia or the like. Fig. 4 is alongitudinal section illustrating the means for supplying an inert gasand for water-cooling the ends of the furnace-tube, and Figs. 5 and 6are respectively a longitudinal and a cross section illustrating themode of watercooling the carbon collars.

Referring to the drawings, 1 is a tube of carbon supplied with carbonterminal rings 2 2 and having collars 3 3 of carbon arranged along itslength at suitable distances apart for supporting and strengthening thetube when it is acted upon by the heat developed in operation. Betweenthe collars 3 3 are packing-rings 4 4, of magnesia or the like, theserings being preferably surrounded by rings or collars 5 5 of asbestos.The whole is surrounded by an insulating-tube 6.

Within the tube 1 a smaller tube 7 is adapted to rotate on its axis, thediameter of the inner tube being small enough to admit of this. Thematerials to be treated in the furnace are inserted within this inner tube,which is accordingly subject to greater Wear than the rest of thefurnace. When this tube is destroyed, it can easily be renewed at smallexpense.

The structure illustrated in Fig. 3 is similar to thatjust described,except that the tube 7 has a lining 8 of magnesia or similar material.

As already stated, I generally prefer to let the tubes 1 and 7 projectbeyond the terminals 2 2 at either end for reasons given above. Thisstructure is illustrated in Fig. 4, wherein the tube 9 represents theinlet for an inert gas, such as hydrogen, this inlet-tube leading to aspace 10 between the tubes 1 and 7. The tube 11 represents the inlet,and 12 the outlet, for a flow of water intended to cool the end of thefurnace. Thisl structure will generally be duplicated at the oppositeend of the furnace. The pipes 11 and 12 are both connected to a box 13,surrounding the tube 1 and bearing at its otherwise-open end against thecarbon terminal 2.

In Figs. 5 and 6 a pipe 14 is shown running in proximity to two of thecarbon collars 3 3 and adapted to carry water for keeping these collarsfrom becoming plastic.

As to the structures shown in the earlier figures of the drawings, itmay be said that the tube 7 may be either of carbon or a material suchas magnesia, the latter material being well adapted for use when lowtemperatures only are to be developed in the furnace. In either case theinner tubes are easily replaceable when they are worn out or burned outin service.

I claim as my invention- 1. An electric tube-furnace having an innertube adapted, when the furnace is in operation, to be freely rotatedtherein.

2. A carbon-tube furnace, consisting of a fixed tube and an inner tubeadapted, when the furnace is in operation, to be freely rotated withinthe fixed tube.

3. A carbon-tube furnace,'consisting of an inner and an outer tubeseparated by an airspace.

4. In an electric furnace, an inner and an outer tube having the spacebetween them filled with a stationary inert gas.

5. In a carbon-tube furnace, a number of supporting-collars surroundingthe tube, and water-cooling devices supplied to the said collars.

6. In a carbon-tube furnace, a suitable carbon tube, collars of carbonsurrounding the same, and cooling devices for the collars.

7. The combination with a tubular electric furnace, of a main tube andan innertube, the space between the tubes being filled with an inertgas, and cooling means applied to oppose distortion of the tube whenhot.

8. A carbon-tube furnace having a main stationary tube and an innerrotatable tube of carbon provided with a lining of magnesia or the like,the inner tube being capable of free rotation within the main tube whenthe 'furnace is in operation.

Signed at New York, in the county of New York and State of New York,this 25th day of March, A. D. 1902.

HENRY NOEL POTTER.

Witnesses:

WM. I-I. CAPEL, GEORGE H. SrocKBRIDGE.

